Is mounting power supply on the bottom of the computer chassis a better design?

JUN 2012

Earliest PS2/ATX power supplies designed in the late 1990’s to early 2000’s had 80mm fans drawing air out, but as the use of 120mm fans became more popular in PCs, most retail power supplies also switched to using 120mm or bigger fans. SilverStone Technology’s first power supply products, the Strider ST360 and ST400, released in 2003 were one of the first examples of this change. The move to bigger fans not only helped lower power supply noise, but due to much greater airflow provided, they became a supplemental tool for cooling the CPU area in a chassis.

The creation of 80 PLUS certification in 2004 and the subsequent push for higher power supply efficiency in the following years resulted in the use of ever slower fans inside the power supplies. Since there was less wasted heat to dissipate in higher efficiency power supplies, their fan controller would regulate the power supply fan to levels so low that they no longer are capable of supplement chassis cooling. In fact, the power supply’s fan controller usually ended up increasing fan speed to cope with the extra heat generated from the CPU area, making supposedly quiet power supplies louder than necessary and reducing their lifetime. To counter this problem, enthusiasts chassis designers started to place power supplies on the bottom of the chassis so they can draw cool air directly from outside of the chassis to reduce power supply fan speed for quieter operation.

For SilverStone engineers, there are many different approaches to designing an optimal chassis. Whenever there are new developments in PC technology that changes the way chassis interacts with the components such as new CPU cooling technique and graphics cards airflow schemes, there will always be chances to improve thermal performance by rethinking the chassis design. So there is no coincidence that SilverStone has historically produced the most diverse form factors and layouts of any chassis manufacturers.

While placing the power supply on the bottom of the chassis is the most common design to ensure power supply can draw cool air from outside of the chassis, it is not the only way. The best air cooling chassis in ATX and Micro-ATX formats are SilverStone’s Fortress FT02 and Temjin TJ08-E respectively, and they both have the power supply located toward the top of the chassis.

Instead of worrying about power supply location, SilverStone engineers focused on the motherboard area, which contains the CPU and the graphics cards, for designing the optimal thermal layout for a chassis. Combining this focus with relentless testing to validate how each computer components affect cooling, SilverStone designed chassis are often tested best in class for thermal performance.

Conclusion: Mounting power supply on the bottom of the chassis is just one way of many for optimal chassis thermal layout and it is not to be used as a gauge to determine chassis design.